This application is a national stage of PCT International Application No. PCT/EP2008/007572, filed Sep. 12, 2008, and claims priority under 35 U.S.C. §119 to German Patent Application No. 10 2007 044 708.8, filed Sep. 18, 2007, the entire disclosures of which are herein expressly incorporated by reference.
The invention relates to a device for the regeneration of a biosensor that includes, on the surface of a carrier, an immobilized and biologically active material designed to interact with a substance to be analyzed.
Biosensors relevant in the context of the present invention are equipped with biological components. The operating principle of a biosensor is based on direct spatial coupling of an immobilized biologically active material located on the surface of a sensor element with an electronic, optical or other transducer, and an electronic amplifier. Such biological materials can be, for example, antibodies, enzymes, organelles, microorganisms or nucleic acids.
The immobilized biological material located on the surface of the sensor interacts with the substance to be analyzed. The interaction may consist of, for example, an interaction between enzyme and substrate, or between an antibody and an antigen, which results in physical alterations, for example of the coating thickness, the refractivity, the absorption of light, the electrical charge or the ion concentration (e.g. change of pH-value) of specific ions in the area of the respective surface. These changes can be measured by measuring devices like optical sensors, amperometric electrodes or field-effect transistors operating based on potentiometric methods.
However, after the measuring procedure, the initial state of the system must be restored. Accordingly, the measurement of the substance to be analyzed with the biosensor is performed in three steps: First, there is the biochemical reaction of the substance to be analyzed by the biological system of the biosensor, after which the reaction is converted into an electric or optical signal, and the signal is then processed and amplified. Consequently, the selectivity and sensitivity of a biosensor is derived from the biological system that is used.
The biological material is arranged on the biosensor by means of a carrier, onto which the material is applied, or on which the material is embedded between two membranes. The biological material can also be immobilized directly on the carrier after the chemical functionalization of the carrier. Furthermore, the biological system can be applied onto a membrane that afterwards is connected with the surface of the transducer. Applications suitable for biosensors in the analysis of water and sewage can be divided into biosensors for the analysis of single components, for the analysis of toxicity and mutagenicity, and for the analysis of the biochemical oxygen demand (BOD). Examples include the measurement of a glucose concentration in the blood of a human being (for example, following an operation). The glucose concentration could be analyzed as the change of the pH-value or as a change of the oxygen concentration as the consequence of glucose-oxidase catalyzed glucose oxidation.
A further biosensor is known for the measurement of the penicillin concentration in a bioreactor (fermenter), in which bacteria strains are cultured that express and secrete penicillin into the culture medium. When the concentration is sufficiently high, the substance can be extracted from the culture medium by organic solvents and after several precipitation reactions. The biological component of the sensor used in this context is the enzyme acylase. The penicillin-cleaving enzyme is embedded in a membrane on which a pH-electrode is located. Once the penicillin concentration in the medium increases, the enzyme catalyzes the formation of increasing amounts of phenyl-acetic acid, and thereby changes the pH-value in the vicinity of the electrode. Hence, it is possible to determine the penicillin concentration based on the pH-value.
Further applications of biosensors concern the analysis of bacteria content in bathwater or sewage. It is possible to apply antibodies directed against certain kinds of bacteria on an oscillating membrane. When the respective bacteria float by the sensor, they attach to the antibodies, thereby diminishing the oscillation of the membrane. A corresponding signal is provided once the oscillation of the membrane falls below a certain value.